Analysis of Small Mammal Populations Inhabiting the Environs of a Low-Level Radioactive Waste Pond*

Analysis of Small Mammal Populations inhabiting the Environs of a Low-Level Radioactive Waste Pond*

K. A. Gano

March 1979

Prepared for the U.S. Department of Energy under Contract No. EY-76-C-06-1830

*This research was performed as part of Rockwell Hanford Operations' Site Characterization Activity, Long-Term Management of Low-Level Waste Program, coordinated by Keith Price.

Pacific Northwest Laboratory Richland, Washington 99352 ACKNOWLEDGMENTS

This study was supported by the Rockwell Hanford Operations Long-Term Management of Low-Level Waste Program under Contracts EY-77-C-06-2130 and EY-76-C-06-1830.

In developing our concepts, we have drawn extensively on the data base, design paradigms and professional experience of staff associated with research programs funded by the Office of Health and Environmental Research of the Department of Energy. Thanks are extended to the people who participated in and contributed to this study. Rockwell scientist D. Paine and Battelle scientists W. H. Rickard, L. E. Rogers, R. G. Schreckhise, G. W. Endres and L. L. Cadwell gave helpful suggestions and advice on data interpretation. C. A. Lee, M. A. Rumble and W. D. Steigers assisted in small mammal trapping and data collection. Dosimeter analysis was performed by F. N. Eichner.

iii This study was designed to determine the kinds of small mammals living adjacent to 216-U-10 Pond, the radiation exposures these mice received, and the level and type of radionuclides assimilated while living next to this pond and the 216-2-19 Ditch. This inforniation will ultimately be used to estimate biologic transport of radionuclides in the pond area.

Four species of mice were trapped and included the Great Basin pocket mouse (~erogmthusparvus ) , deer mouse (~eromjscusmaniculatus ) , house mouse us musculus) , and the western harvest mouse (~eithrodontomysmegalotis). Animals were collected throughout the study and composite tissue samples were analyzed by gamma spectrometry. Also, an analysis for 238P~, 239,240P~ and 241Am was performed. The most abundant garrlliia emitter was 137Cs with the highest levels occurring at three trapping locations: one near the 216-2-19 Ditch and two locations adjacent to the pond. House mice captured near the 216-2-1 9 Ditch showed the highest 1evels with one gastrointestinal (GI) tract sample having 1600 pCi 137Cs/g dry weight. Four tissue types from resident mice were analyzed for Pu and Am concentrations. The tissues analyzed were fur-skin, liver, lung, and muscle-bone. The highest concentration detected was 2.03 pCi 239,240P~/gdry weight in a fur-skin sample from house mice captured on the meadow transect near the pond.

Results from radiochemical analyses of mouse tissues showed that pocket mice have the lowest concentrations of radionuclides. They were also less frequently trapped on the two riparian transects near the pond. This may be attributed to food and habitat preference. Pocket mice generally prefer the Artemisia tridentata-Bromus tectorwn vegetation type to ripari an habi tats such as the pond and ditches.

Another part of this study involved dosimeters implanted in resident mice to determine gamma exposure. Analyses revealed that mice living in the meadow transect adjacent to the pond receive the highest exposure. Again, house mice had the highest, with an average 54.9 R/yr.

Dosimeters were placed in the soi 1 along the trapping transects to measure gamma and thermal neutron exposure rates at each dm of soil to a depth of 5 dm. This sh~wedthe stratification of exposure rates in a 5-dm soil profile. The top decimeter of soil had the highest exposure rate with a mean of 75 R/yr in the meadow. Neutron dose in the soil was also highest near the surface with 37 mrad/yr average in the meadow. CONTENTS

ACKNOWLEDGMENTS SUMMARY . LIST OF FIGURES LIST OF TABLES IIVTRODUCT IOIV . SITE DESCRIPTION . METHODS . RESEARCH AND ANALYSIS . SPECIES COMPOSITION AND RELATIVE ABUNDANCE . RADIOCHEMICAL ANALYSES . Gamma-Emi tting Nucl ides . Plutonium Analysis . Food Habits GAMMA EXPOSURES TO SMALL MAMMALS . EDAPHIC EXPOSURE RATES . Neutron Exposure in the Soil . CONCLUSIONS . LITERATURE CITED . APPENDIX A APPENDIX B APPENDIX C APPENDIX D APPENDIX E LIST OF FIGURES

Map of Hanford Area Showing U-Pond . 2 U-Pond Small Mammal Transects 3 Anesthetized Pocket Mouse Being Imp1 anted with Dosimeter Packet . 6 Dowel Showing Surface Location of Dosimeters Used to Measure Soil Exposure . 8 Concentrations of Plutonium and Americium in Composite House Mouse Samples . 12 Concentrations of Pl utonium and Americil~m in Composite Pocket Mouse Samples . 12 Concentrations of Pl utonium and Americium inCompositeDeerMouseSamples . 13 Concentrations of Pl utonium and Americium in Composite Harvest Mouse Samples . 13 Gamma Exposure to Mice Living Along U-Pond and Control Transects . 16 Gamma Exposure to Soil Along U-Pond Transects 17 Cross Section of Z-19 Ditch Showing Location of Soil Dosimeter Probes . 19

viii LIST OF TABLES

Total Number of Animals Captured and Percentage of Each Species on U-Pond and Control Transects . U-Pond Plutonium Analysis on Whole Mice Mean Gamma Exposures to U-Pond Mice in R/yr . Mean Gamma Exposure to Soil on U-Pond Transects in R/yr Mean Neutron Exposure to Soil on U-Pond in mrad/yr Composite Sample Using Like Tissues from Two or More Animals of Same Species, pCi 137Cs/g Dry A.l.l Fur-Skin Samples . A. 1.2 Liver Samples A. 1 .3 Kidney Samples . A.1.4 Lung Samples . A.1.5 GI Tract Samples . A. 1.6 Muscle-Bone Samples . Composite Samples Other than 137~s,pCi/g Dry A.2.1 Sampling Period 9-10April '75 . A.2.2 Sampling Period 6-7 May '75 . A.2.3 Sampling Period 23-24 October '75 U-Pond Samples Col 1ected During 1976-77 and Analyzed as Individual Animals, pCi/g 137Cs/g Dry . U-Pond Samples Coll ected During 1976-77 and Analyzed as Individ~alAnimals, pCi/g Dry ( Samples Other than 137Cs ) . Isotopic Plutonium and Americium Analysis of U-Pond Mice Using Composite Samples B. 1.1 Concentrations of 238P~/gDry . B. 1 .2 Concentrations of 239p~/gDry . B.1.3 Concentration~of~~~Am/gDry. Mean Gamma Exposure to Small Mammals at U-Pond in mR/wk Gamma Exposure to U-Pond Mammals in mR/wk . Gamma Exposure in Soil Along U-Pond Transects in Roentgens Per Year . D.2 Neutron Exposure in Soil Along U-Pond Transects in mrads Per Year . . D-3 D.3 Mean Gamma Exposure to Soil on U-Pond Transects in Roentgens Per Year . . D-4 E.l Total Number of Individual Animals Captured Each Month . E-1 E.2 Average Number of Animals Captured on U-Pond Transects Per Trap Session . . E-3 INTRODUCTION

Information concerning species composition, concentration of radionuclides taken up by the various species, and external doses of gamma radiation is essen- tial in determining the environmental impact of waste management areas on small mammal populations. Small mammals are potential vectors in the transport of radionucl ides away from waste management areas because they provide a food base for many larger, more mobile secondary consumers such as snakes, raptors, bad- gers, racoons, skunks, and coyotes. For this reason it is important to determine the types and the quantities of nuclides being concentrated by mice living on waste management areas. Also of concern is the exposure rate to the biota on these areas (Energy Research and Development Administration, 1975).

This study was designed to gather information on small mammals living adjacent to 216-U-10 Pond. Radiation exposures to the mice were investigated along with the level and type of radionucl ides being assimilated. This information will ultimately be used to estimate biologic transport of radionuclides in the pond area.

To accompl ish this objective the following approach was used:

1. Species composition was investigated for mice living near 216-U-10 (U-Pond), a liquid waste disposal site.

2. Tissue samples taken from mice living in the vicinity of 216-U-10 were analyzed for radionuclide content to determine concentrations.

3. Dosimeters were implanted in mice living in the vicinity of the trapping transects on the study areas to provide a means for determining external gamma exposures.

4. To establish exposure distribution in a 5-dm soil profile, dosimeters were buried at 1 dm increments along the transect lines.

This report describes results of these analyses. Appendix A contains results from tissue analysis for gamna emitters, and Appendix B provides summaries of tissue analysis for plutonium and americium-241. Appendix C includes exposure rates of gamma radiation to mice living near the various transects. Appendix D provides information on the stratification of gamma and thermal neutron radiation doses in a 5-dm soil profile along each transect and Appendix E contains information on trapping results.

SITE DESCRIPTION

The study areas are located on the Department of Energy's Hanford Site in Benton County, southcentral Washington (Figure 1). These areas consist of the U-Pond study site, specifically 216-U-10 (Figure 2), located within the con- fines of the 200 West perimeter fence, a control plot near U-Pond, and an additional control site on the Arid Lands Ecology (ALE) Reserve at Rattlesnake Springs, establ ished to correspond with the riparian vegetation at U-Pond. FIGURE 1. Map of Hanford Area Showing U-Pond U-Pond was established in 1944 in a shallow depression in the 200 West Area of the Hanford Site. Its function was to receive low-level radioactive wastes, primarily cooling water, and laundry waste water. The pond presently receives water from three major sources: a plutonium processing plant via 216-2-19 Ditch, a laundry where protective clothing is washed (via 216-U-14 Ditch), and an evaporator crystal 1izer plant which reduces 1iquid rad-wastes to salt cakes via 216-U-14 Ditch.

U-Pond is the oldest 1iquid waste disposal site on the Hanford Site. Since its origin, a diverse riparian vegetation has developed, creating an attractive habitat for many animals otherwise not common to this arid environment (Fitzner and Rickard, 1975).

TRAPS

x SOIL TLD LOCATIONS

U-POFID FOREST TRANSECT

FIGURE 2. ti-Pond Small Mammal Transects METHODS

Trap lines were established at the U-Pond study site using Sherman live traps. Four transects were set up near the pond. These transects each contained 10 traps. There were two different habitat types represented. A trap line along the Z-19 Ditch and one along the U-14 Ditch represented a desert habitat of sagebrush-cheatgrass with access to free water. The riparian habitat adjacent to the pond was represented by two transects, one in the small delta region between the two ditches (~eadowtransect), and one near the south end of the pond in a wooded area, the Forest transect (Figure 2).

Two control transects were located in noncontaminated areas away from the pond. One control transect was located inside the 200 West per-inieter fence in a sagebrush-cheatgrass area approximately 114 mile from U-Pond. It contained two lines of 10 traps each for a total of 20 traps. The second control transect on theArid Lands Ecology Reserve at Rattlesnake Springs contained 40 traps. Sixteen trapping sessions were conducted at the U-Pond study site and control transects. Trapping commenced in April 1975 and ended in July 1977.

The first phase of the study investigated radionuclide concentrations in the small mammals living near the pond. The trap lines were operated during April, May and October 1975, and the mice submitted for radiochemical analysis. After each trap session the animals were brought into the lab and separated by species and transect. They were then dissected into various tissues with each like sample of same species and location combined to make composite samples. For example, all the livers from pocket mice captured on the Z transect during one trap session were combined to make one sample.

During the first sample session in April 1975, the composite sarr~ples con- sisted of muscle-bone, fur-skin, head, feet-tail, lung, liver, kidney, testes, ovary, and gastrointestinal tract. During the sample periods of May and Octo- ber 1975, four of the sample types were discontinued. The "head" and the "feet-tail" samples were not used because in both cases there were inseparable internal and external structures, e.g., bone, ~iiuscleand fur-skin on the "feet- tail" sample, making it impossible to determine the location of detectable radionuclides. The testes and ovary samples were also discontinued due to insufficient tissue mass to obtain val id counting results. Therefore, the samples used in the following two sample sessions were fur-skin, liver, lung, kidney, gastrointestinal tract, and muscle-bone (the remaining carcass).

The samples were oven-dried at 50°C for 48 hr and then analyzed by gamma spectrometry. Samples from each transect with significant 137Cs concentrations above control values were selected and analyzed for plutonium concentrations. Samples from May and October sessions were analyzed for specific plutonium and americium, i.e., 238P~,239-240~~, and 241Am by LFE Environmental Analy- sis Laboratories, Richmond, California.

Tissue samples were taken throughout the study peri~dfor radiochemical analysis and included whole body samples for plutonium analysis. Two other

Following the operation the mice were returned to their respective points of capture and released. Approximately 1 month later the trap lines were operated again and the recovered TLDs exchanged. Concurrently, newly captured mice were -irr~pl anted with TLDs.

The TLD 700s used in this study were calibrated for exposure dose in air with a 226Ra source. Therefore, all exposure data from TLD 700s are reported in roentgens (R). Totally accurate measurements of absorbed doses in U-Pond mice are extremely difficult to interpolate. Calculations necessary to determine absorbed dose from known exposed dose employ a conversion factor which uses the effective atomic number of the irradiated medium along with the energies of the ionizing radiations. The following expression is used for this conversion when the photon energy and mass absorption coefficient of the exposed medium are known (Arena, 1971 ).

Rads (absorbed dose) = [0.869 '/ Of R (exposed dose) EIp of air where the p/p values are the mass absorption coefficients for the absorbing material and air. The mass absorption coefficients are functions of the energy of the incident photons and the atomic number of the absorbing medium.

If one assumes that the energies of the incident photons at U-Pond were equal to 0.1 MeV, and only soft tissues of the mice were considered then the mass absorption coefficients are 0.0252 cm2/g for the material and 0.0231 cm2/g for air (NBS Handbook 85, 1964). The absorbed dose would then be equal to 0 0252 cm2/ rads = 10.869 -1 R = (0.95) R Dosimeters were also placed in the soil along the transect lines. There were five locations on each transect. At each location, aluminum tubing, 5.5 dm long by 1.9 cm in diameter and a wall thickness of approximately 1 mm, was driven into the soil. Dosimeters were attached to a wooden dowel at 1-dm intervals and the dowel placed inside the aluminum tubing (Figure 4). The dosimeter locations started at the soil surface and went to a depth of 5 dm.# Along with TLD 700s, which are primarily for detecting gamma radiation, TLD 600s were also used at each depth. The TLD 600 is capable of detecting gamma and thermal neutron radiation and was employed to check for neutron radiation in the soil. Detectable neutron radiation would indicate the presence of trans- uranic elements which undergo spontaneous fission.

The response of TLD 600s to thermal neutron exposure is related through the calibration to the response of tissue if tissue were present. Therefore, all thermal neutron exposures are reported in mrads.

RESEARCH AND ANALYSIS

The trapping effort had four main objectives. The first was to determine species composition of the small mammals 1iving in the vicinity of U-Pond and the two contributing ditches; the second was to quantitatively measure the uptake of nuclides, and the third was to determine the gamma exposure to small mammals inhabiting the radiation zones adjacent to the pond. The fourth part of this study enabled edaphic exposure rates to be checked by placing dosimeters at certain levels in the soil. The following text includes the field work and corresponding analyses.

SPECIES COMPOSITION AND RELATIVE ABUNDANCE

There were four species of mice trapped at the U-Pond site. They included the Great Basin pocket mouse, Perognuthus parvus, deer mouse, Peromyscus mani- cuZatus , house mouse, Mus muscuZus, and the western harvest mouse, Reithrodon- tomys megaZotis .

The relative abundance of each species varied according to the habitat of each transect. The vegetation on the U-Pond control transect is described as sagebrush-cheatgrasslsandberg bluegrass type (Daubenmire, 1970; Cline, et al., 1975). The most frequently trapped small mammal on this transect was the pocket mouse with 43 individual animals and second was the deer mouse with 28 individuals (Table 1). The transects along U- and Z-Ditches appear to have vegetation similar to the control transect with the exception of nearby free water and a very 1-iniited and narrow riparian zone. The major small mammal species trapped along these transects was the pocket mouse comprising 82% of the individuals captured at U-Ditch and 69% at Z-Ditch (Appendix E-1). Deer mice comprised the majority of individual s captured in the riparian vegetation of the Meadow and Forest transects with 37% and 46% respectively. Species composition was most diverse at these two transects with all four species represented in both (Table 1).

The control transect located at Rattlesnake Springs was established to correspond with the riparian vegetation transects at U-Pond. It also served as an added control for deer mice to supplement data collected on the control transect near U-Pond. The trapping effort at Rattlesnake Springs yielded 36 deer mice, making it an effective control for this species.

TABLE 1. Total Number of Animals Captured and Percentage of Each Species on U-Pond and Control Transects

R.S. U-Pond Control (a) Control Z-Di tch Meadow U-Ditch Forest n% n% n% n% n% n% Pocket Mouse 43 61 45 69 17 23 51 82 6 10 Deer Mouse 36 97 28 39 19 29 28 37 9 15 27 46 House Mouse 13 1 2 26 35 2 3 21 36 Harvest Mouse 4 5 5 8

(a) Rattlesnake Springs Control n Number of individuals caught % Percent of individuals caught on each transect RADIOCHEMICAL ANALYSES

Radiochemical analyses were conducted for both gamma-emitting nuclides and plutoni um.

Gamma-Emittina Nuclides

Composite samples representing six tissue types were analyzed for gamma- emi tting nucl ides. The tissues used were fur-skin, 1iver, kidney, 1ung, gastrointestinal tract, and muscle-bone. Samples from each of the transects were represented during the three sampling periods.

The most abundant gamma emitter detected from the U-Pond samples was 137Cs (Appendix A). The gamma scan indicated that the next most abundant nuclide in the samples was lo6Ru. However, this nuclide was represented in only one out of three sampling sessions. The May 1975 sampling session showed lo6Ru with an average of 220 pCi/g dry.

The highest content of 137Cs was found in a house mouse GI tract composite and contained 1600 + 82 pCi/g dry. This sample came from the Z-Ditch transect. The remaining five tissue types from this species on this transect also showed high values, with the lowest being 470 pCi/g dry. Next in order from the highest to lowest were the western harvest mouse, the deer mouse, and the Great Basin pocket mouse. The harvest mouse was represented in the samples orlly twice, once in the Meadow and once in the Forest transect. The 137Cs levels, for these samples, however, compared quite closely with those of the house mice from these transects and sampling sessions (Appendix A-1 through A-6).

The deer mice were the most completely represented species and occurred on all transects. On three of the transects, the Z-Ditch, Meadow, and the Forest, deer mice were collected during each of the sampling sessions. Upon comparing the three sessions, results from the October session in most cases appears to have higher concentrations than the other two sessions for this mouse. This suggested trend can especially be seen in the muscle-bone sample for deer mice. The replication of this trend in other tissue samples of deer mice corroborates this suggestion. Affir~iiationof this trend may prove to be very -important as an aid to monitoring the uptake of radionuclides by deer mice; however, additional work on the seasonal variations of nuclide uptake by deer mice is needed to con- firm this possible trend.

The pocket mouse samples, in contrast, show very little activity from the three transects they represented in this sarr~plingscheme. These transects were the control, Z-Ditch and U-Ditch, all of which contained similar levels of radiocesi urn.

In a different analysis, mice were randomly taken throughout the year and analyzed as individual animals. The samples were divided into two tissue types: 1 ) hide, feet and tail, and 2) remaining carcass. In this analysis, levels of 137~sfor deer mice closely resembled the figures from the composite samples. The locations yielding deer mouse samples for this analysis were again the Z-Ditch, Meadow, and Forest transects. Although pocket mice were not captured during the first three sampling sessions on the Meadow and Forest transects, they were represented on these transects in this sampling scheme. This time the quantity of cesium detected in pocket mice closely resembled that of the deer mice from the same transects. Two pocket mice from the Meadow had levels exceeding that of the deer mice ranging from 138 to 332 pCi/g dry as opposed to 8.5 to 265 pCi/g dry (Appendix A-13).

The gamma scan data from these two sampling schemes show the Fleadow and ' . the Forest transects as the areas with the highest levels of radiocesium uptake by the small mammals sampled. Next are the ditches which are represented by deer mice, house mice, and harvest mice. Activity levels in pocket mouse tissues taken from the ditches are not significantly different from those on the control transect. The similarity of the results from individual samples and the composites indicates that combining of 1-ike tissues probably did not obscure any high values of individual tissue.

Plutonium Analysis

Four composite sample types were used for an isotopic plutonium analysis. They were fur-skin, liver, lung, and muscle-bone. The sample qroups used were selected from the gamma scan results as the ones containing l3 Cs activity. Also, an effort was made to represent all transects at least once.

Results from the analyses indicated that the amount of plutonium being taken up by small mammals was very low. Figures 5a, 5b, 5c, and 5d show concentrations for the four species trapped. The highest concentrations came from house mice living in the Meadow area and along the Z-19 Ditch (Figure 5a). A composite fur-skin sample from six house mice living in the Meadow yielded the highest value with 2.03 pCi 239-240P~/gdry. Samples representing the other three species in this analysis showed very low values for plutonium and americiu~iiof < 0.5 pCi/g dry. In another analysis for plutonium, whole mice were analyzed-using deer mice from Z-19 Ditch and house mice from the Meadow. In this analysis the samples were tested for 238P~and 239+240P~. The results for 238P~showed levels very near background but for 239+240P~ the deer mice from Z-19 exhibited levels that appeared slightly above the control values which average 0.98 pCi/g dry (Table 2).

The data from these analyses indicate that of the four species of mice tested, the house mouse, the deer mouse, and the harvest mouse have the greatest opportunity for uptake of radionuclides at the U-Pond site.

Food Habits

The most probable explanation for the higher concentrations of the above three species may be related to their food habits and environmental or habitat preference. The omnivorous deer mouse is an opportunistic feeder taking advan- tage of whatever food is available (W-illianis, 1959; Flake, 1973; Kritzman, 1974; HOUSE MI

FUR-SKI

kZM FC ;;ZMFC d'ZMF

- 0.8 LUNG MUSCLE-BONE >- oh - 2-Z-DITCH E M -MEADOW r=" 0.4 - F - FOREST u, C - CONTROL 0.2 - O'O -*

FIGURE 5a. Concentrations of Plutonium and Americium in Composite House Mouse Samples POCKET MICE

0.8 1 FUR-SKIN LIVER > 0.6 n E P.- 0.4 U - U-DITCH 2 Z - 2-DITCH 0.2 C - CONTROL 0.0 - -UZC -UZC uzc

1.0 0.8 1 LUNG i::1 MUSCLE-BONE

FIGURE 5b. Concentrations of Plutonium and Americium in Composite Pocket Mouse Samples DEER MICE

- FUR-SKIN LIVER -

- 0.4

- 02 -- UFC [b,-UFC UFC

1.0 - 1.0 -

0.8 - 0.8 - LUNG MUSCLE-BONE 0.6 - 0.6 - n U - & 0.4 - 0.4 - U-DITCH \.- F - FOREST U, C - CONTROL 0.2 - 0.2 -

0.0 - - 0.0 - - - - UFC -UFC UFC U FC U FC LI FC 238~u 239~u 241~m 238~u 239~u 241~rr FIGURE 5c. Concentrations of Pl utonium and Americi um in Composite Deer Mouse Samples

HARVEST MICE 1.o 1.0

F - FOREST - 0.8 - C - CONTROL 0.3 - 0.6 0.6 - Ll VER D FUR-SKIN E - - .-P 0.4 0.4 U, 0.2 - 0.2 -

- - - F 0.0 - 0.0 - FC FC FC FC -FC 23gPu 239pu 241A, 23gPu 239pu 241A,

1.0

LUNG MUSCLE-BONE > 0.6 1 1 1 0.4 U, 02

(1_- 0.0 - - - O.O FC FC FC FC FC FC Z38pu 23gpu 241Am 238pu 23qPu 241Am

FIGURE 5d. Concentrations of Pl utonium and Americium in Coniposi te Harvest Mouse Samples TABLE 2. U-Pond Plutonium Analysis on Whole Mice

- - 238~u -239+24OPu Species x Dry Wt g x pCi/g dry x pCi/g dry Deer Mouse Z-Di tch 4.5 0.10 (0.005) 0.98 (0.05) n=3 Control 5.0 0.13 (0.006) 0.12 (0.006) n=l House Mouse Meadow 4.8 0.03 (0.002) 0.07 (0.003) n=2 Control 3.8 0.03 (0.002) 0.06 (0.003) n=l

( ) = Counting error.

Johnson, 1975). The presence of free water and an abundance of riparian vegetation enhances the availability of food for this mouse. MacMillen (1964) showed that deer mice, when fed a diet of only dry seeds, had a mean time till death of about 20 days. This supports the theory that they must satisfy their water requirements by eating green vegetation, arthropods, or by drinking free water. The deer mice living at U-Pond most likely do all three.

The house mouse is likewise an omnivorous feeder, eating seeds, fruits, vegetables, meat and arthropods (Ingles, 1965; Brooks, 1973). This mouse also seeks the lush vegetation and free water of the ditches and pond to satisfy its water requirements. The western harvest mouse also selects a habitat with dense vegetation, especially grasses near water. The major food items are seeds, succulent stems, fruits, and insects (Hall and Kelson, 1959; Ingles, 1965; Burt and Grossenheider, 1976). In an arid environment, U-Pond provides an ideal habitat for this mouse.

The pocket mouse, on the other hand is primarily a granivore and can sub- sist solely on a diet of dry seeds (Schmidt-Nielson et al., 1948; Kritzman, 1974). This species does not need free water but occasionally eats green vegetation during the spring months when available. Pocket mice also prefer the dry sandy soil ot tne surrounding noncontaminated desert for constructing their deep and elabo- rate burrow systems (Scheffer, 1938; Hall, 1946). This probably explains the low activity levels observed in pocket mice at the U-Pond site.

GAMMA EXPOSURES TO SMALL MAMMALS

Small mammals associated with the U-Pond study site were also investigated for external garrnla exposure. The procedure involved surgically implanting thermoluminescent dosimeters (TLDs) subcutaneously and releasing the animal to be caught at a later date. The technique proved very successful; overall, 49% of the TLDs implanted were recovered. Dosimeters recovered from animals 1iving in the Meadow area exhibited the highest exposures (Figure 6). The three species represented there were, from highest dose to lowest, the house mouse, pocket mouse, and deer mouse with mean doses of 55 R/yr, 43 R/yr, and 21 R/yr, respectively (Table 3). The Forest transect was also represented by all three species and likewise showed significant exposures above background. The Z-Ditch was the only other transect to show animals receiving significant exposures. The animals being exposed on this transect were deer mice. Pocket mice were also represented on Z Transect claim- ing Illore recaptures than any other species or 1ocation. Thirty-two dosimeters were recovered giving a mean dose of 0.14 R/yr. This figure agrees with the pocket mouse exposures on the control transect of 0.09 R/yr. The exposure data from U-Ditch were represented by only one species, the pocket mouse, whose doses were slightly higher than the control with 0.35 R/yr. Deer mice from both control transects had identical exposures of 0.07 Rlyr.

Dosimeters were not recovered from house mice on Z Transect, U Transect, or the control transects and deer mice on U Transect. Capture frequencies for house mice are very low even in an area of higher density. This is attributed to the seeming sixth sense of house mice for shying away from traps (Brooks, 1973) along with a probable low density. Personal experience has shown that harvest mice are very difficult to trap and even more difficult to retrap. A1 though six animals were successfully implanted with TLD packets, there were no recaptures and, consequently, no exposure rate data were obtained. The number of deer mice captured along U Trench was also very low throughout the study period.

From the dosimeter data gathered in this study, it becomes apparent that mice living in the Meadow and Forest transects received the most significant gamma exposure. This can be attributed to the fact that at one time the pond was much larger, encompassing these areas. When the pond receded it left sedi- ments containing radionuclides exposed and readily available to terrestrial plants and animals.

The effect from the highest exposure rate recorded at U-Pond (1.47 R/wk to a pocket mnuse; see Appendix C-5) would probably be very slight or even immeasurable. A decrease in the number of circulating lymphocytes in the blood is a very sensitive measure of radiation exposure. Acute doses of 5-25 rads can cause a drop in the number of these cells in rats (Casarett, 1968). However, with a maximum chronic dose of approximately 1.4 rad per week, a decrease in lymphocytes may not be detectable. No obvious abnormalities were noticed in mice during this study. Further investigation of histopathological changes is needed to determine the effects of very low chronic exposures to U-Pond mice.

EDAPHIC EXPOSURE RATES

Dosimeters placed in the soil along the trapping transects revealed that the location of the strongest gamma exposures is the top decimeter of soil (Figure 7). The highest exposures came from the Meadow transect with a mean of 75 Rlyr in the first decimeter. The levels of exposure diminished rapidly with depth, going down to 1.5 R/yr at 5 dm (Table 4). This trend is consistent FIGURE 6. Gamma Exposure to Mice Living Along U-Pond and Control Transects

TABLE 3. Mean Gamma Exposures to U-Pond Mice in R/yr Pocket Mouse Deer Mouse House Mouse Rlyr + S.E. Rlyr + S.E. Rlyr + S.E. R. S. C~ntrol(a) 0.07 2 0.003 U. P. Control 0.09 + 0.005 0.07 + 0.003 Z-Di tch 0.14 + 0.01 5.74 + 4.83 U-Di tch 0.35 + 0.11 Forest 4.02 + 2.5 2.92 + 0.41 13.5 + 8.8 Meadow 42.6 + 7.32 21.1 + 1.9 54.9 + 1.7

(a) Rattlesnake Springs Control. LN EXPOSURE RATES (R/yr)

XI + 7 0 cn-i n, mcn. - rl-

- .000000.~ . . 000000-J OOOOOW V4WPLnrn- - 1:; on all the transects at U-Pond. The control transect shows the exposure rate to be consistent from the surface to 5 dm. The higher exposure rates to the soil in the Meadow and Forest areas concur with the higher exposure levels of the animals living on these areas.

Neutron Exposure in the Soil

U-Pond historical ly has received 1ow-1 eve1 re1eases of plutoni um processing wastes a1 ong with many other transuranics at marginally detectable levels (Emery and Gar1 and, 1974). 'The pond receives plutonium processing effluents from the 234-5 plant via the Z-19 Ditch. Although processing wastes continu- ously flow into the ditch, releases of plutonium are usually low level and on an intermittent basis. For this reason, dosinieters capable of detecting thermal neutron radiation were incorporated in the soil dosimeter probes along the transects.

The Meadow area showed the highest neutron exposure again in the first decimeter of soil with an average of 37 mradlyr (Table 5). The forest transect showed quite a reduced dose from the Meadow with 4.8 mrad/yr at 1 dm and again tapering down with depth. The Z-19 Ditch was the only other location sampled that showed a neutron exposure. In this case, however, the trend of highest to lowest from the surface down was somewhat reversed. The highest average level detected here was 7.8 mrad/yr and was at 4 dm. The lowest was 1.9 mrad/yr at 1 dm and the surface. This reverse trend is probably a function of the dosimeter location near the ditch. On this transect, the aluminum tubing containing the dosimeter was placed halfway down the slope of the ditch. This made the bottom locations on the dowel closer to the level of water in the ditch (Figure 8). The doses along U-14 Ditch and the control transect were similar at all depths, indicating background exposures.

TABLE 5. Mean Neutron Exposure to Soil on U-Pond in mrad/yr Soil Depth - Meadow Forest Z -Transect U Transect - Control in Decimeters x + S.E. i -+ S.E. x ? S.E. i + S.E. x + S.E. 0 37.1 + 16.2 4.1 + 1.58 1.87 + 1.25 0.48 + 0.02 0.26 + 0.0 FIGURE 8. Cross Section of Z-19 Ditch Showing Location of Soil Dosimeter Probes CONCLUSIONS Trapping results along with the radiochemical analyses indicate that the areas of most concern at U-Pond were the Z-19 Ditch and the riparian zone associated with the ,pond. A1 1 species of mice captured in these areas (except pocket mice along Z-Ditch) accumulated concentrations of radiocesium significantly above background. The number of individuals representing each species on a transect appeared to vary according to habitat preference. Pocket mice preferred the noncontaminated sagebrush-cheatgrass habitat adjacent to the ditches over the riparian . I habitat surrounding the pond, as indicated by trapping results. Thus, the fewer numbers of this species living near the pond reduced the transfer potential for pocket mice. House mice and deer mice preferred the denser vegetation around the pond and thus pose a greater threat for biological transfer due to their food habits and greater numbers in this area. The potential for biological transfer of radionuclides to a small mammal species and up through the food chain is proportional to the number of individuals of that species present and the availability of radionuclides in an area. Further information should be gathered to determine the origin of the radionuclide concentrations in these animals. The biological transfer pathway of radionuclides to mice could be further examined by diet analysis. A follow-up on the results could include a radiochemical analysis of the food items detected. The emphasis of waste management at this site could then be directed toward the primary biological transfer organisms. The radiation exposure data from thermoluminescent dosimeter (TLD) implants showed the highest exposures to animals living along the transects near the pond. The three species for which data were obtained (house mice, deer mice and pocket mice) each had exposures above background. This trend agrees with the radiochemical analysis data from these areas. Animals living along the Meadow and Forest transects appear to be accumulating above background concentrations of radionuclides and external radiation exposures. This also appears to be true for mice living along the two ditches, but to a lesser degree. In most instances the values from the ditches appear only slightly above background. Results from dosimeters placed in the soil along the trapping transects showed the greatest exposure in the surface decimeter of soil. The transects with the highest exposure were those closest to the pond. This means that the surface decimeter of soil near the pond probably has the highest concentrations of radionuclides. This low level contamination could be readily available to vegetation which provides a food base for the inhabiting mice. It could also account for the higher exposure rates to mice living near the pond. Deer mice captured along Z-19 Ditch received higher exposure rates than corresponding soil dosimeters. This is due to the location of the soil dosimeters along one bank of the ditch. These higher exposure rates indicate that the deer mice preferred the dense vegetation near the bottom of the ditch where higher exposure rates exist. The water and lush emergent vegetation covering the ditch provided a good habitat for deer mice. LITERATURE CITED

Arena, V. 1971. Ionizing Radiation and Life. C. V. Mosby, St. Louis, MO.

Brooks, J. E. 1973. A Review of Commensal Rodents and Their Control. IVew York State Department of Heal thy Bureau of Rodent Control , A1 bany, NY, pp. 405-453.

Burt, W. H., and R. P. Grossenheider. 1976. A Field Guide to the Mammals. Houghton-Miff1 in Company, Boston, MA.

Casarett, A. P. 1968. Radiation Biology. Prentice-Hall , Inc. Englewood Cliffs, NJ.

Cline, J. F., D. W. Uresk, and W. H. Rickard. 1975. Characterization of Plant Communities Adjacent to the B-C Cribs Controlled Area and REDOX Pond Areas on the 200 Area Plateau. BNWL-1916. Battelle, Pacific Northwest Laboratories, Richland, WA.

Daubenmire, 1970. Steppe vegetation of Washington. Wash. Agric. Exp. Tech. 62, 131 pp.

Emery, R. M., and T. R. Garland. 1974. The Ecological Behavior of Plutonium and Americium in a Freshwater Ecosvstem:" Phase 11. BNWL-1879. Battelle, Pacific Northwest Laboratories, Rich1and, WA.

Energy Research and Development Administration. 1975. Final Environmental Statement. 2 Vol s. ERDA-1538, Waste Management Operations, Hanford Reserva- tion, Richland, WA.

Fitzner, R. E. , and W. H. Rickard. 1975. Avifauna of Waste Ponds, ERDA Hanford Reservation, Benton County, Washington. BNWL-1885. Battel ley Pacific Northwest Laboratories, Richland, WA.

Flake, L. D. 1973. Food habits of four species of rodents on a short-grass prairie in Colorado. J. Mammal. 54:636-47.

Hall, E. R. 1946. Mammals of Nevada. Univ. Calif. Press, Berkeley and Los Angeles.

Hall, E. R., and K. R. Kelson. 1959. The Mammals of North America. Ronald Press Co. , New York.

Ingles G. L. 1965. Mammals of the Pacific States. Stanford Univ. Press, Stanford, CA. Johnson, M. K. 1975. Interspecifi c Association of Peromyscus manicuZatus , Pero.qnathus parvus, and SpermophiZus tmnsendi on the Arid Lands Ecology Reserve Examined by Diet Overlap and Related Data. BNWL-1929. Battel le, Pacific Northwest Laboratories, Richland, WA, 50 pp.

Kritzman, E. G. 1974. Ecological relationships of Peromyscus manicuZatus and Perognuthus parvus in eastern Washington. J. Mammal. 55:172-88.

MacMillen, R. E. 1964. Population ecology, water relations, and social behavior of a southern California semi-desert rodent fauna, Univ. Cal ifornia Pub1 . ZOO^. 71:l-66.

National Bureau of Standards. 1964. Physical Aspects of Irradiation. NBS Handbook No. 85. U.S. Government Printing Office, Washington, DC, p. 3.

Scheffer, T. H. 1938. Pocket mice of Washington and Oregon. U.S.D.A. Tech. Bull etin 608.

Schmidt-Nielsen, B., D. Schmidt-Nielsen, A. Brokaw, and H. Schneiderman. 1948. Water conservation in desert rodents. J. Coll. Comp. Physiol. 32: 331 -360.

Williams, 0. 1959. Food habits of the deer mouse. J. Mammal. 40:415-19. APPENDIX A

DETECTABLE GAMMA-EMITTING NUCLIDES TABLE A.1. Composite Sample Using Like Tissues from Two or More Animals of Same Species, pCi 137Cs/g Dry

A. 1 .1 Fur-Skin Samples

TRANSECT

Sample Sessions Pocket Mouse Deer Mouse Harvest Mouse House Mouse

CONTROL Apr-i1 0.44 (0.44) - - May - - - - October - - 10.0 (3.6) R.S. October 1.3 (1 .2)

Z-DITCH Apri 1 1.7 (1.1) - - May 0.99 (0.66) 8.7 (1 .O) October - - 12.0 (4.9) MEADOW Apri 1 May October

U-D ITCH Apri 1 2.5 (2.5) May 2.5 (0.78) 33.0 (1.7) October 3.1 (1.6)

FOREST Apri 1 May October

R.S. - Rattlesnake Springs Control ( ) - Counting error - - - Values less than detection limits TABLE A. 1 . (Continued) A.1.2 Liver Samples

TRANSECT

Sample Sessions Pocket Mouse Deer Mouse Harvest Mouse House Mouse

CONTROL Apri 1 - - - - May - - - - October 3.3 (2.2) - - R.S. October

Z-DITCH Apri 1 - - 2.8 (2.6) May - - 9.8 (2.8) October 5.8 (3.2) 11 .O (9.7)

MEADOW Apri 1 May October

U-DITCH Apri 1 - - Yay 62.0 (5.1) October 1x0 (4.9)

FOREST Apri 1 May October

R.S. - Rattlesnake Springs Control ( ) - Counting error -- - Values less than detection limits TABLE A.1. (Continued)

A.1.3 Kidney Samples

TRANSECT 1975 Sample Sessions Pocket Mouse Deer Mouse Harvest Mouse House Mouse

CONTROL Apri 1 9.5 (5.5) - - May - - - - October - - - - R.S. October - -

Z-DITCH Apri 1 27.0 (26.0) - - May - - 18.0 (8.8) October 18.0 (13.0) - - MEADOW Apri 1 May October

U-DITCH April 54.0 (45.0) May - - 50.0 (12.0) October - - FOREST Apri 1 May October

R. S. - Rattlesnake Springs Control ( ) - Counting error - - - Values less than detection limits TABLE A.1. (Continued)

A. 1.4 Lung Samples

TRAN SECT 1975 Sample Sessions Pocket Mouse Deer Mouse Harvest Mouse House Mouse

CONTROL Apri 1 - - 124.0 (80.0) May - - - - October 15.0 (9.1) 45.0 (24.0) R.S. October - - Z-DITCH Apri 1 May October

MEADOW Apri 1 May October

U-DITCH Apri 1 May October

FOREST Apri 1 May October

R. S. - Rattlesnake Springs Control ( ) - Counting error - - - Values less than detection limits TABLE A.1. (Continued)

A.1.5 GI Tract Samples

TRANSECT

Saniple Sessions Pocket Mouse Deer Mouse Harvest Mouse House Mouse

CONTROL Apri 1 1.3 (0.9) - - May - - - - October 1.8 (1 .o) - - R.S. October 0.72 (0.71)

Z-DITCH Apri 1 - - - - May - - 13.0 (3.7) October 2.6 (1.3) 9.7 (6.8)

MEADOW Apri 1 May October

U-DITCH April 14.0 (4.7) May 7.1 (1.6) 122.0 (3.2) October 8.4 (2.8)

FOREST Apri 1 May October

R.S. - Rattlesnake Springs Control ( ) - Counting error - - - Values less than detection limits TABLE A. 1. (Continued)

A. 1 .6 Muscle-Bone Samples

TRANSECT

Sample Sessions Pocket Mouse Deer Mouse Harvest Mouse House Mouse

CONTROL Apri 1 0.53 (0.25) - - May - - 0.54 (0.40) October 0.67 (0.52) - - R.S. October - - Z-DITCH Apri 1 May October

MEADOW Apri 1 May October

U-DITCH Apri 1 - - May 5.2 (0.5) 68.0 (2.2) October 8.2 (1 -0) FOREST Apri 1 May October

R.S. - Rattlesnake Springs Control ( ) - Counting error - - - Values less than detection limits A.2. Composite Samples Other Than 137Cs, pCi/g Dry A.2.1 Sampl ing Period 9-10 April '75

Species & Sampl e 40K 54Mn 6oCo 6 5Zn 9521" lo6Ru 144Ce U-POND CONTROL TRANSECT Deer Mouse Muscl e-Bone Fur-Skin Head

Pocket Mouse Lung Muscl e-Bone 13 (3.6)

Z-DITCH TRANSECT Deer Mouse Fur-Ski n GI Tract Head

Pocket Mouse Muscl e-Bone Head

FOREST TRANSECT Deer Mouse Liver

MEADOW TRANSECT Deer Mouse Kidney Muscl e-Bone

House Mouse Feet-Tai 1 Head

Harvest Mouse Head TABLE A. 2. (Continued) A.2.2 Sampling Period 6-7 May '75

Species & Sampl e 40K 54Mn 60Co 65Zn 95Zr lo6Ru 14Ve

11-POND CONTROL TRANSECT Deer Mouse Liver Kidney Lung GI Tract

Pocket Mouse Liver Kidney GI Tract

2-DITCH TRANSECT Deer Mouse Liver GI Tract

Pocket Mouse Lung GI Tract 19 (5.1)

U-DITCH TRANSECT Deer I4ouse Kidney

!Jr:~ ,-et :;:.,use Lung GI Tract rluscle-Bone

FOREST TRANSECT Deer Mouse Liver Lung Muscle-Bone

House Mouse Liver Kidney Lung GI Tract bluscle-Bone

MEADOW TRANSECT Deer Mouse Liver Muscle-Bone

House Mouse Liver Kidney Lung TABLE A.2. (Continued)

A.2.3 Sampling Period 23-24 October '75

Species & -Sample '+OK S4Mn 60Co 65Zn 95Zr l06Ru l4?e U-POND CONTROL TRANSECT Deer Mouse Muscle-Bone 45 (22)

Pocket Mouse Fur-Skin 28 (11) Liver 67 (31) Lung Muscle-Bone 20 (6.9)

Z-DITCH TRANSECT Deer Mouse Muscle-Bone 9.1 (3.5)

House Mouse Fur-Skin Liver

Pocket Mouse Fur-Skin 2.3 (0.9) 3.7 (1.4) I.luscle-Bone 18 (6.4) U-DITCH TRANSECT Pocket Mouse Fur-Skin 51 (22) 8.2 (2.9) Lung 182 (67) Ptuscle-Bone 29 (13) 2.6 (1.1) 4.0 (1.7)

Deer Mouse Fur-Skin Kidney

House House Fur-Skin

Harvest IAouse Muscle-Bone

MEADOW TRANSECT Deer Mouse Kidney Lung

RATTLESNAKE SPRINGS CONTROL Deer Mouse Liver 5.7 (2.8) Muscle-Bone 22 (6.4) TABLE A.3. U-Pond Samples Collected During 1976-77 and Analyzed as Individual Animals, pCi 137~s/gDry

TLD Sampl e Pres . Number Pocket Mouse Deer Mouse House Mouse

U-POND CONTROL TRANSECT

U-DITCH TRANSECT

Z-DITCH TRANSECT 76UM05-a 05- b 76UM08-a 08- b 76UM10-a 10-b Yes 77UM01 -a 01 -b Yes 77UM02-a 02-b Yes 77UM03-a 03- b Yes 77UM04-a 04- b Yes 77UM17-a 17-b Yes 77UM18-a 18-b TABLE A. 3. (Continued) TLD Sampl e Pres. Number Pocket Mouse Deer huse House Mouse

FOREST TRANSECT

FEADOW TRANSECT

( ) - Counting error - - - Below detection limits a - Sample consists of skin, fur, feet, tail b - Sample consists of remaini ng carcass TABLE A.4. U-Pond Samples Collected During 1976-77 and Analyzed as Individual Animals, PcI/g Dry

Samples Other Than 137Cs

Species & Samp 1e 40K 54Mn 6oCo G5Zn q5Zr l06Ru 144Ce

U-POND CONTROL TRANSECT Pocket Mouse 77UM10-a 10-b 77UMll-a 11-b 77UM12-a 12-b 77UM13-a 13-b

U-DITCH TRANSECT Pocket Ibouse 77UM05-a 05-b 77UM21-a 21-b 33 (14) 77UM22-a 22-b 56 (15)

House House 77UM14-a 14-b

Z-DITCH TRANSECT Deer Mouse

Pocket [louse 76UM10-a 10-b 77UM01 -a 01-b TABLE A.4. (Continued)

Species & Sample 40K 54Mn 6oCo 6 5Zn 95Zr 106Ru ' 44Ce

FOREST TRANSECT Pocket Mouse

Deer llouse 76UMll -a 11-b 77UM07-a 07- b 77UM08- a 08- b 77UM09-a 09-b 77UM16-a 16-b MEADOW TRANSECT Deer Mouse

Pocket Mouse

( ) - Counting error Sample consists of skin, fur, feet, tail a - A-15 b - Sample consists of remaining carcass

TABLE C.2. (Continued)

Forest Transec t Cont. U-Ditch Transect

House Mouse Pocket Mouse Pocket Mouse

Sex Dose Sex Dose Sex Dose Sex Dose

a" 426.4 a* 33.8 a* 7.8 a" 3.0 a* 88.5 f 221.2 9 4.2 9 2.1 9 19.7 9 4.3 a" 2.4 9 32.3 oT 3.0 a* 11.6 a" 3.9 9 4.4 a" 4.0 a* 4.8

a" 10.9 a" 5.2

a" 1.9 a" 46.8

a" 2.3 a" 5.7 a* 2.1 9 3.0 ------____------n = 2 4 20 2 + S.E. = 258 + 170 76.8 + 48.3 6.7 + 2.2

Range = 426 to 89 19.7 to 221 1.9 to 46.8

APPENDIX D

GAMMA AND NEUTRON EXPOSURES TO SOIL ALONG U-POND TRANSECTS TABLE D.1. Gamma Exposure in Soil Along U-Pond Transects in Roentgens Per Year

CONTROL TRANSECT Dosimeter Locations - Soil Depth #1 #2 #3 # 4 # 5 X S.E.

0 dm .084 .073 .073 .073 .084 .077 .002 1 dm .084 .084 .084 .084 .084 .084 0.0 2 dm .lo4 .lo4 .094 .094 .084 .096 .003 3 dm .073 .lo4 .094 .lo4 .084 .092 .006 4 dm -104 .lo4 .094 .lo4 .084 .098 .004 5 dm .I15 .094 .094 .lo4 .I15 .lo4 .005

Z 'TRANSECT Soil Depth

U TRANSECT Soil Depth TABLED. 1. (Continued)

Dosimeter Locations FOREST TRANSECT - Soil Depth # 1 #2 #3 # 4 # 5 x S. E.

0 dm 14.2 4.50 11.9 .542 2.69 6.78 2.67 1 dm 23.2 3.19 8.88 .230 2.71 7.64 4.14 2 dm 6.23 .824 3.41 .I25 .814 2.28 1.14 3 dm 1.90 .334 1.70 .I15 .407 .892 .376 4 dm .699 .354 4.59 .I15 .292 1.21 .850 5 dm .354 .208 ,303 .I35 .365 .273 .044

MEADOW TRANSECT Soil Depth TABLE D.2. Neutron Exposure in Soil Along U-Pond Transects in mrads Per Year

CONTROL TRANSECT Dosimeter Locations Soil Depth # 1 $2 # 3 $4 # 5

0.26 0.26 0.26 0.26 0.31 0.31 0.31 0.26 0.26 0.37 0.31 0.37 0.37 0.26 0.37 0.31 0.31 0.26 0.37 0.31 0.31 0.31 0.31 0.37

Z TRANSECT Soil Depth

U TRANSECT Soil Depth TABLE 0.2. (Continued)

FOREST TRANSECT Dosimeter Locations Soil Depth #1 #4 # 5 x S.E.

0.68 1.62 4.1 1.58 0.37 1.41 4.8 2.69 0.31 0.63 1 .52 0.63 0.31 0.47 0.63 0.15 0.26 0.37 0.34 0.02 0.37 0.42 0.36 0.03

MEADOW 'TRANSECT Soil Depth

TABLE D. 3. Mean Gamma Exposure to Soi 1 on U-Pond Transects in Roentgens Per Year

Soil Depth *adow Forest Z-Transect U-Transect Control in Decimeters i + S.E. i + S.E. x + S.E. x + S.E. --i + S.E. APPENDIX E

SUMMARIES OF TRAPPING DATA TABLE E.1. Total Number of Individual Animals Captured Each Month

Apr 1975* May 1975* Oct 1975* CZMUF ------ACZMUF -CIMUF - Pocket Mouse 9 3 1 5 6 5 6 6 3 Deer Mouse 2 4 2 2 65146 212 2 House Mouse 2 6 4 1 4 Harvest Mouse 1 1

Mar 1976* May 1976 Jun 1976 Jul 1976 R.S. MUFMUF -----CZMUF Pocket Mouse 41391 8 5 3 9 2 Deer Mouse 5 513417 942 2 House Mouse 1 1 4 5 6 2 Harvest Mouse 3 1

Aug 1976 Sep 1976 Nov 1976 ZMUF C R.S. C Z M U F Pocket Mouse 7 3 8 2 11 8 5 7 Deer Mouse 2212 5 5 326 2 House Mouse 1 3 1 Harvest Mouse 1

*Animals captured during months were sacrificed for radiochemical analysis R.S. = Rattlesnake Springs Control C = U-Pond Control Z = Z Trench M = Meadow U = U Trench F = Forest TABLE E. 1. (Continued)

Dec 1976 Feb 1977 Mar 1977 -ZMUF - - - -R.S. -----CZMUF Pocket Mouse 4 1 6934 Deer Mouse 3413 12 42314 House Mouse 3 2 1 Harvest Mouse

Apr 1977 May 1977 Jul 1977* . . R.S. C Z M U F --R.S. Z !!A -F /Mt4F- Pocket Mouse 314462 13611 2 6331 Deer Mouse 18 3 17 1 7 513 House Mouse 1 Harvest Mouse 1 1

* Animals captured during months were sacrificed for radiochemical analysis. TABLE E.2. Average Number of Animals Captured on U-Pond Transects Per Trap Session*

Rattlesnake U-Pond Springs Control Z-Trench Meadow U-Trench Forest - - - - - n x S.D. n x S.D. ---n x S.D. ---n X S.D. ---n x S.D. ---n x S.D. Pocket Mouse 8 7 2.5 11 7.1 3.5 13 1.9 2.2 13 5.5 3.2 13 0.9 0.9

Deer Mouse 4 10.5 5.8 8 4.3 2.4 11 2.2 1.7 13 3.3 2.1 13 0.8 1.1 13 2.9 1.8

House Mouse 11 0.1 0.3 13 1.9 2.2 13 0.2 0.4 13 1.5 1.9

Harvest Mouse 13 0.3 0.9 13 0.4 0.5

*Data from Apr, May, Oct 1975, Mar 1976, and Jul 1977 were omitted due to selective trapping for radiochemical analysis. m n = Number of trapping sessions 9 = W S.D. Standard Deviation DISTRIBUTION

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